Based upon our previous studies of the pathogenesis of periodontal disease in monoinfected rats and our current light and electron microscopic investigation of the effects of experimentally induced inflammation on the oral connective tissues of conventional rats we propose to conduct morphometric studies of the inflammatory infiltrate and connective tissue remodelling in the periodontal tissues of gnotobiotic rats monoinfected with a variety of bacteria. Particular emphasis will be placed on the previously unrecognized role of fibroblasts in the degradation of polymerized collagen and in the recently discovered increase of this activity in the immediate vicinity of osteoclasts. The possibility that a similar inflammatory cell-fibroblast relationship exists will be examined in experimentally induced inflammation. We propose to study the cellular localization of a specific Actinomyces surface antigen and corresponding antibody in the periodontium, lymphnodes and parotid gland of monoinfected rats by means of light and electron microscopic immunochemistry. We hope to be able to relate the penetration of the antigen to the inflammatory process. Part of this research is concerned with elucidating the role of fibroblasts in collagen degradation. Studies will be conducted in vitro with isolated periodontal ligament fibroblasts. The role of microfilaments in the attachment to and phagocytosis of collagen fibrils will be studied. Morphometric studies of repair in the periodontal ligament will be conducted to further characterize the cellular mechanism of collagen and bone remodelling.